[libc-commits] [libc] [libc] fix -Wconversion (PR #77384)

[Nick Desaulniers via libc-commits]

https://github.com/nickdesaulniers created https://github.com/llvm/llvm-project/pull/77384

Fixes the following from GCC:

    llvm-project/libc/src/string/memory_utils/op_x86.h:236:24: error:
    conversion from ‘long unsigned int’ to ‘uint32_t’ {aka ‘unsigned int’} may
    change value [-Werror=conversion]
      236 |   return (xored >> 32) | (xored & 0xFFFFFFFF);
          |          ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

Link: https://lab.llvm.org/buildbot/#/builders/250/builds/16236/steps/8/logs/stdio
Link: https://github.com/llvm/llvm-project/pull/74506


>From 546b0db3f078a3ae222d2bb9ec0f4c0b2feb7bda Mon Sep 17 00:00:00 2001
From: Nick Desaulniers <ndesaulniers at google.com>
Date: Mon, 8 Jan 2024 14:11:20 -0800
Subject: [PATCH] [libc] fix -Wconversion
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Fixes the following from GCC:

    llvm-project/libc/src/string/memory_utils/op_x86.h:236:24: error:
    conversion from ‘long unsigned int’ to ‘uint32_t’ {aka ‘unsigned int’} may
    change value [-Werror=conversion]
      236 |   return (xored >> 32) | (xored & 0xFFFFFFFF);
          |          ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

Link: https://lab.llvm.org/buildbot/#/builders/250/builds/16236/steps/8/logs/stdio
Link: https://github.com/llvm/llvm-project/pull/74506
---
 libc/src/string/memory_utils/op_x86.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libc/src/string/memory_utils/op_x86.h b/libc/src/string/memory_utils/op_x86.h
index 1a20659c178cd1..3d2eb13fa302ad 100644
--- a/libc/src/string/memory_utils/op_x86.h
+++ b/libc/src/string/memory_utils/op_x86.h
@@ -233,7 +233,8 @@ template <> LIBC_INLINE uint32_t neq<__m512i>(CPtr p1, CPtr p2, size_t offset) {
   const auto a = load<__m512i>(p1, offset);
   const auto b = load<__m512i>(p2, offset);
   const uint64_t xored = _mm512_cmpneq_epi8_mask(a, b);
-  return (xored >> 32) | (xored & 0xFFFFFFFF);
+  return static_cast<uint32_t>(xored >> 32) |
+         static_cast<uint32_t>(xored & 0xFFFFFFFF));
 }
 template <>
 LIBC_INLINE MemcmpReturnType cmp_neq<__m512i>(CPtr p1, CPtr p2, size_t offset) {